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Keep in mind that it's frowned upon by some Pythonistas for several reasons:

If you need to do something different depending on the condition, then use a normal if statement instead. We use the expression to compute the value, and then do something with it. We can use it when we are in a 'one value or another' situation, where we will do the same thing with the result, regardless of whether the condition is met. Think of the conditional expression as switching between two values. # this is just for demonstration purposes. Or for example to return a value: # Of course we should just use the standard library `max` You can, however, use conditional expressions to assign a variable like so: x = a if True else b Similarly, because it is an expression, the else part is mandatory: # Invalid syntax: we didn't specify what the value should be if the But please don't write code like that it will quickly become very difficult to understand.)

(In 3.8 and above, the := "walrus" operator allows simple assignment of values as an expression, which is then compatible with this syntax. Synta圎rror: cannot assign to conditional expression > # it can't be on the left-hand side of `=`. > # The `(1 if False else x)` part is actually valid, but > # Python parses this as `x = (1 if False else y) = 2` This means you can't use statements such as pass, or assignments with = (or "augmented" assignments like +=), within a conditional expression: > pass if False else pass

Note that conditionals are an expression, not a statement. This allows short-circuiting because when condition is true only a is evaluated and b is not evaluated at all, but when condition is false only b is evaluated and a is not evaluated at all.įor example: > 'true' if True else 'false' If condition evaluates to True, then a is evaluated and returned but b is ignored, or else when b is evaluated and returned but a is ignored. The expression syntax is: a if condition else bįirst condition is evaluated, then exactly one of either a or b is evaluated and returned based on the Boolean value of condition.